Bump version in master to 0.5-dev so built dev versions will say so
Bump version in master to 0.5-dev so built dev versions will say so

Signed-off-by: Ying Li <f39392f1e2d21dabc2bc5ab11d2bf832bde87b60@docker.com>

andrewhsu/notary,endophage/notary,vdemeester/notary,docker/notary,umayr/notary,endophage/notary,HuKeping/notary,umayr/notary,endophage/notary,vdemeester/notary,dqminh/notary,dqminh/notary,HuKeping/notary,johnsandiford/notary,docker/notary,jfrazelle/notary,johnsandiford/notary,vdemeester/notary,jfrazelle/notary,umayr/notary,andrewhsu/notary,dqminh/notary,HuKeping/notary,johnsandiford/notary,jfrazelle/notary,andrewhsu/notary,docker/notary